the influence of new and modernized gnss on positioning ... · pdf filethe influence of new...

ALLSAT Open, June 22, 2006, Hannover, Germany

The Influence of New and Modernized GNSS on Positioning within RTK Networks

Gerhard Wübbena

Geo++® GmbH30827 Garbsen

Germanywww.geopp.com


Outline

● New GNSS and Modernization● Satellite Availability● New Signals and Ambiguity Resolution● Simulations● Do we still need RTK Networks ?● Challenges for Network RTK Software● Summary


New GNSS and Modernization

● GPS will provide new (civil) signals (L2C, L5, L1c)● GLONASS will have „Full Constellation“ in 2007/2008● Galileo will be operational in 2011 ?● Galileo will provide up to 5 frequencies with different signals● All together more than 75 GNSS satellites will be available


Satellite Availability

● Satellite Visibility Plots for Hannover, June 14, 2006 using– Current GPS Almanach– Galileo Constellation (Walker 27/3/1):

● 3 Orbit Planes with 9 Satellites each● Altitude: 23616 km● Inclination: 56°● Ground Track repeating every 10 siderial days

– GLONASS Constellation (Nominal Constellation)● 3 Orbit Planes with 8 Satellites each● Altitude: 19100 km● Inclination: 64.8°● Ground Track repeating every 8 siderial days


GPS Sky-Plot for Hannover 2006-06-14


Galileo Sky-Plot for Hannover 2006-06-14


GLONASS Sky-Plot for Hannover 2006-06-14


GNSS Sky-Plot for Hannover 2006-06-14


GNSS Visible Satellites for Hannover 2006-06-14


GNSS PDOP for Hannover 2006-06-14


GNSS HDOP for Hannover 2006-06-14


GNSS VDOP for Hannover 2006-06-14


GNSS Improvement of Availability in Obstructed Areas


New Signals and Ambiguity Resolution

● 3rd GPS Frequency (L5)● Up to 5 Galileo Frequencies● New Codes (L2C, L1C?, Galileo) with improved Accuracy

– Code Noise Level in the order of 10 cm or better– Reduced Multipath Errors

● New Carrier and Code Phase Linear Combinations with 3 and more Frequencies

● Literature indicates (very) Optimistic Ambiguity Resolution Performance– TCAR– MCAR– ...


Linear Combinations of Carrier Phases

● Linear Combination with Integer Coefficients (n,m,k,...)●

● Apparent Frequency:●

● Apparent Wavelength:●

● Ionospheric Influence relative to L1

n ,m , k ,=n∗1m∗2k∗3

f n ,m ,k ,=n∗ f 1m∗ f 2k∗ f 3

n ,m , k ,=c

f n ,m , k ,

dI n ,m , k ,=

nf 1 mf 2 kf 3

n∗ f 1m∗ f 2k∗ f 3∗ f 1

2∗dI 1


Linear Combinations of Carrier Phases

● Ionospheric Amplification Factor●

●

●

● Noise: Phase Noise s [radians] ●

● Caution: Amplification of Biases– MP (Near Field, Far Field)– Antenna– Keep n,mk, small

sn ,m , k ,=n∗nm∗mk∗k∗s

vI n ,m , k ,=

nf 1 mf 2 kf 3

n∗ f 1m∗ f 2k∗ f 3∗ f 1

2


Some GPS Linear Combinations

L1 L2 L5 Lambda VI1 VI/Lambda Sigma Sigma-Cyc

1 0 0 0.1903 1.0000 5.2550 0.0009 0.0048 0 1 0 0.2442 1.6469 6.7440 0.0012 0.0048 0 0 1 0.2548 1.7933 7.0372 0.0012 0.0048 1 -1 0 0.8619 -1.2833 -1.4889 0.0058 0.0068 0 1 -1 5.8610 -1.7186 -0.2932 0.0396 0.0068 1 0 -1 0.7514 -1.3391 -1.7821 0.0051 0.0068 1 -5 4 2.0932 -0.6616 -0.3161 0.0648 0.0309 1 -4 3 1.5424 -0.9397 -0.6093 0.0376 0.0243 1 -3 2 1.2211 -1.1020 -0.9025 0.0218 0.0179 1 -2 1 1.0105 -1.2083 -1.1957 0.0118 0.0117

C1C2C5 C0

L0 L1 L2 L5L1,-1,0

L1,0,-1

L0,1,-1


Some Galileo Linear Combinations

L1 E5a E5b E5 E6 Lambda VI1 VI/Lambda Sigma Sigma-Cyc 1 0 0 0 0 0.1903 1.0000 5.2550 0.0009 0.0048 0 1 0 0 0 0.2548 1.7933 7.0372 0.0012 0.0048 0 0 1 0 0 0.2483 1.7032 6.8583 0.0012 0.0048 0 0 0 1 0 0.2515 1.7474 6.9466 0.0012 0.0048 0 0 0 0 1 0.2344 1.5178 6.4742 0.0011 0.0048 1 -1 0 0 0 0.7514 -1.3391 -1.7821 0.0051 0.0068 1 0 -1 0 0 0.8140 -1.3051 -1.6032 0.0055 0.0068 1 0 0 -1 0 0.7815 -1.3219 -1.6915 0.0053 0.0068 1 0 0 0 -1 1.0105 -1.2320 -1.2192 0.0068 0.0068 0 1 -1 0 0 9.7684 -1.7477 -0.1789 0.0660 0.0068 0 1 0 -1 0 19.5368 -1.7702 -0.0906 0.1319 0.0068 0 1 0 0 -1 2.9305 -1.6498 -0.5630 0.0198 0.0068 0 0 1 -1 0 19.5368 -1.7252 -0.0883 0.1319 0.0068 0 0 1 0 -1 4.1865 -1.6079 -0.3841 0.0283 0.0068 0 0 0 1 -1 3.4477 -1.6286 -0.4724 0.0233 0.0068 0 2 -3 0 1 29.3052 -0.7690 -0.0262 0.5235 0.0179 0 4 -1 -4 1 29.3052 -0.6340 -0.0216 0.8159 0.0278 1 -1 1 3 -4 4.5085 0.0858 0.0190 0.1139 0.0253 1 4 1 -3 -3 3.9074 -0.0012 -0.0003 0.1119 0.0286 3 -5 0 0 3 0.1119 0.0002 0.0018 0.0035 0.0313 3 -3 2 -4 3 0.1119 0.0007 0.0064 0.0037 0.0327 4 -3 -1 1 0 0.1087 -0.0003 -0.0031 0.0027 0.0248


Simulations

● 2 Scenarios– 500 km Interstation Distances within Network

● Residual Troposphere for Rover Position 2 cm RMS ZD● Residual Ionosphere 0.6 m RMS per Satellite

– 100 km Interstation Distances within Network● Residual Troposphere for Rover Position 2 mm RMS ZD● Residual Ionosphere 0.2 m RMS per Satellite

– 3 Frequency GPS– 3 Frequency Galileo (L1, E6, E5a+b)– 2 Frequency GLONASS– Code Noise 0.4 m, Code MP 2 m RMS, 60 s Correlation Length– Phase Noise 0.002 m, Phase MP 0.004 m RMS, 60 s Cor.Length


Simulations

● Overall Results (both Networks)– Instantaneous Ambiguity Fixing >90%– Fixing within 20 s: 100%


Accuracy (Sparse Network 500 km)


Accuracy (Network 100 km)


Do we still need RTK Networks with full GNSS Constellations● Answer: YES

– Height Accuracy– Support for Rovers with Single / Dual Frequency Receivers– Support for Rovers in Areas with Obstructions– Redundancy

● Network Density may be Reduced– Rovers should estimate Residual Troposphere


Challenges for RTK Networks and Network RTK Software

● Non-Homogeneous Reference Stations / Satellites– Receivers with different capabilities of Signal Tracking– Satellites with different Signals (GPS)

● Network should support as many signals as possible– Serve all Rovers

● Software must be flexible (mixed Receivers/Satellites/Signals)● Representation of Error Sources should switch

– From Observation Space Representation (OSR) (RTCM)– To State Space Representation (SSR)– > Reduction of Bandwidth– > Support for all Signals


Challenges for Network RTK Software and RTK Networks

● Rigorous Network Adjustment Requires State Parameters:– Satellite Orbits (3 or 6 per Satellite)– Satellite Clocks (2 or 3 per Satellite)– Satellite Signal Biases (2 per Satellite per Signal – 1)– Ionosphere (adquate Model + #Rx * #Sv)– Troposphere (1 or 2 per Receíver)– Receiver Signal Biases+Clock (2 per Signal -1 +1)– Receiver Coordinates (3)– Carrier Phase Ambiguities (1*RCVs*SATs*Signals)– ==> 30 Stations, 30 Satellites, 3 Signals/Satellite (Mean)– ==> (14*30 + 100 + 60 + 90 + 90 + 3600 = 4360 Parameters)– ==> Improved Filter Algortihms Required!


Summary

● Full GNSS Constellations Provide– Improved Availability– Improved Accuracy– Fast Ambiguity Fixing over longer Distances using new Signals

and high number of Satellites● RTK Networks will still be necessary● Complexity of Network Setup and Software will increase


Thank you for your attention!

the influence of new and modernized gnss on positioning ... · pdf filethe influence of new...

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